Voluntary dataset on affinities of 60,000+ Reddit users, recorded in 2010. From the enclosed readme file:
"I filtered the list of votes for the list of users that gave us permission to use their data. For the curious, that's 67,059 users: 62,763 with "public votes" and 6,726 with "allow my data to be used for research"...I'm trying to use it to build a recommender, and I've got some preliminary source code. I'm looking for feedback on all of these steps, since I'm not experienced at machine learning."